Mercuria carrillorum Miller, García-Guerrero & Ramos, 2023

Miller, Jonathan P., Delicado, Diana, García-Guerrero, Fernando, Khalloufi, Noureddine & Ramos, Marian A., 2023, Morphology and taxonomic assessment of eight genetic clades of Mercuria Boeters, 1971 (Caenogastropoda, Hydrobiidae), with the description of five new species, European Journal of Taxonomy 866 (1), pp. 1-63 : 33-38

Mercuria carrillorum Miller, García-Guerrero & Ramos sp. nov.

urn:lsid:zoobank.org:act:E9ED5EC6-E8DC-42ED-8EDC-2D2322296196

Figs 20–22 ; Supp. file 2: Tables S14–S18

Diagnosis

Shell ovate-conic; periostracum dark brown to blackish; protoconch microsculpture granulated; aperture obliquely ovate; central radular tooth formula (3)4-C-4(3)/1-1; female genitalia with bursa copulatrix elongate, ca 3 times as long as wide; seminal receptacle elongate; distal end of the penis ca 1.5 times as long as penial appendix, darkly pigmented; penial appendix ovate, pigmented to the distal part, medially positioned on the inner edge of the penis; nervous system pigmented, elongate (mean RPG ratio = 0.63); cerebral ganglia approximately equal in size.

Etymology

Named after the family of Miguel Carrillo Pacheco who instilled his scientific curiosity and passion for malacology and in recognition for his help with the fieldwork conducted across Spain, France and Portugal.

Type material

Holotype SPAIN • sex unknown (dry preserved); Cádiz, Jerez de la Frontera, Canuto de la Gallina , Montes de Propios ; MNCN 15.05/200175H .

Paratypes SPAIN • 33 specs (preserved in ethanol 80%, 10 dissected and 4 processed for DNA sequencing); same collection data as for holotype; MNCN 15.05/94748 • 16 specs (preserved in ethanol 80%); same collection data as for holotype; MNCN 15.05/94750 • 17 specs (preserved in ethanol 80%); same collection data as for holotype; MZB 2021-2796 • 2 specs (dry preserved); same collection data as for holotype; NHMW 113527 • 2 specs (dry preserved); same collection data as for holotype; RMNH. MOL.507924 • 1 spec. (dry preserved); same collection data as for holotype; JPM-586 • 2 specs (dry preserved); same collection data as for holotype; MCP • 2 specs (dry preserved); same collection data as for holotype; MCP.

Additional material examined

SPAIN – Cádiz • 30 specs; Jerez de la Frontera, Montes de Propios , stream in Canuto de las Palas ; MNCN 15.05/94751 • 3 specs; same collection data as for preceding; MNCN 15.05/94749 . – Málaga • 3 specs; Manantial de los Doce PIlares spring; MNCN-ADN 110673 to 110675 .

Additional locality information provided in Supp. file 1: Table S1.

Type locality

Stream in Canuto de la Gallina, Montes de Propios, Jerez de la Frontera, Cádiz, Spain. 36.587509° N, 5.574243° W; 379.72 m a.s.l.

Description

MEASUREMENTS. Holotype: SL = 3.04 mm, SW = 2.26 mm, SL/SW = 1.34, AH = 1.43 mm, SL-LBW = 0.73 mm, WBW = 1.78 mm, AL = 1.44 mm, AW = 1.07 mm, WPW = 1.03 mm, WAW = 0.52 mm.

SHELL. Ovate-conic, whorls 4–5, height 2.4–3.8 mm, width 1.8–2.7 mm ( Fig. 20A–F ; Supp. file 2: Table S14); periostracum dark brown to blackish; protoconch of 1.5 whorls, ca 350 µm wide, nucleus ca 150 µm wide ( Fig. 21A–B ); protoconch microsculpture granulated ( Fig. 21C ). Teleoconch whorls slightly convex, separated by a deep suture; body whorl large and convex, occupying about two-thirds of the total shell length; aperture obliquely broad ovate, complete; inner lip slightly thicker than outer lip; aperture margin straight; outer lip slightly sinuated; umbilicus narrow, not covered by the inner lip ( Fig. 20A, C–F ).

OPERCULUM. As for the genus, orangish to brown, about 2 whorls; muscle attachment oval, located near the nucleus ( Fig. 20G–H ).

RADULA. Length intermediate, ca 600 µm long (20% of total shell length), containing about 70 rows of teeth. Central tooth formula (3)4-C-4(3)/1-1, central cusp V shaped, cutting edge slightly concave ( Fig. 21D–E ). Lateral tooth formula (4)3-C-3(4), central cusp V shaped and slightly longer than the central tooth one. Inner marginal teeth with 12–16 cusps; outer marginal teeth with 25–27 cusps ( Fig. 21F ). Radular data were collected from the following specimens: MNCN 15.05/94748 and MNCN 15.05/94750 from Canuto de la Gallina, Cádiz and MNCN 15.05/94749 and MNCN 15.05/94751 from Canuto de las Palas, Cádiz.

PIGMENTATION AND ANATOMY. Animal brownish to pale brown ( Fig. 22E ); head and tentacles brown, eye lobes unpigmented; snout and neck weakly pigmented; snout longer than wide, approximately parallel-sided, with medium distal lobation. Pallial tentacle present. Ctenidium occupying almost the total length of the pallial cavity; 22–26 gill filaments, broad, triangular, and fused at the base by an epithelium ( Fig. 22G ). Osphradium elongate, more than 3 times as long as wide, positioned opposite to the middle of the ctenidium. Stomach almost as long as wide with two chambers about equal in size (Supp. file 2: Table S16); style sac longer than wide, with the unpigmented intestine surrounding its distal part before continuing on as a straight rectum ( Fig. 22H ).

MALE GENITALIA. Prostate gland small, bean-shaped, about 2 times as long as wide, connected by the posterior vas deferens to a convoluted seminal vesicle and the testis ( Fig. 22F ). The distal end of the penis ca 1.5 times as long as penial appendix (Supp. file 2: Table S18), darkly pigmented, gradually tapering, attached to the neck behind the right eye; penial appendix ovate, pigmented on the distal part, medially positioned on the inner edge of the penis ( Fig. 22C–E ).

FEMALE GENITALIA. Glandular oviduct 2.5 times as long as wide; albumen gland longer than capsule gland ( Fig. 22A ); bursa copulatrix elongate, ca 3 times as long as wide (Supp. file 2: Table S17); bursal duct shorter than bursa copulatrix; renal oviduct unpigmented, highly coiled with three loops; seminal receptacle elongate, with a short duct, positioned on the distal part of the renal oviduct at the junction with the bursal duct ( Fig. 22B ).

NERVOUS SYSTEM. Pigmented, elongate (mean RPG ratio = 0.63; Supp. file 2: Table S15); cerebral ganglia approximately equal in size; pleuro-supraoesophageal connective ca 9 times as long as pleuro-suboesophageal one ( Fig. 22I ).

Ecology and distribution

Restricted, as the species has been found at only three localities, all in Cádiz and Málaga, Spain. Very small specimens (probably juveniles) of the species were collected for the first time at Manantial de los Doce Pilares Spring, Málaga in 2015. However, we were unable to find any specimens at this locality during a subsequent sampling trip in 2017.

Contrary to other species of Mercuria , M. carrillorum sp. nov. lives in streams with very low conductivities, ranging from 80–179 µS/cm. Co-occurring species, though at low abundances, are Ancylus fluviatilis O.F. Müller, 1774 and Galba truncatula (O.F. Müller, 1774) , except the stream in Canuto de la Gallina in which only M. carrillorum is found (Félix Ríos Jiménez pers. com.).

Remarks

Mercuria carrillorum sp. nov. differs from the phylogenetically closely related species M. egarensis sp. nov. by having a more ovate than a high-spired shell, a smaller and more pigmented penial appendix, an elongated bursa copulatrix (from pyriform to elongate in M. egarensis ), a smaller radular ribbon, a larger number of cusps on the central radular tooth and the presence of a pallial tentacle.

Mercuria carrillorum sp. nov. resembles M. felixi sp. nov. and M. balearica in terms of shell shape ( Fig. 3 ) but differs from them in other features. The new species has an ovate, pigmented penial appendix that is shorter than the distal end of the penis, whereas in M. felixi , the distal end of the penis and appendix are about equal in length. In M. balearica , the penial appendix is longer than the distal end of the penis, which is triangular and extremely pigmented. These species also differ in the lengths of the bursa copulatrix (longer in Mercuria carrillorum than in M. balearica ) and the pleuro-supraoesophageal connective (longer in M. felixi ). The major difference in the radula is the number of cusps on the outer marginal teeth: M. carrillorum has considerably more cusps (25–27) than M. balearica and M. felixi .

The sequence divergence of COI for Mercuria carrillorum sp. nov. and the other Iberian congeners ranged between 1.3% (with M. egarensis sp. nov.) and 8% (with M. felixi sp. nov.). With a divergence of 8.9%, the most distantly related species was the Tunisian M. saharica Letourneux & Bourguignat, 1887 ( Miller et al. 2022)

Figures

Fig. 20. Shells and operculum of Mercuria carrillorum Miller, García-Guerrero & Ramos sp. nov. A–B. Holotype (MNCN 15.05/200175H), frontal and lateral views. D, G–H. Paratypes (MNCN 15.05/94748). C. Manantial de los Doce Pilares Spring, Málaga, Spain.D. Stream in Canuto de la Gallina, Montes de Propios, Jerez de la Frontera, Cádiz, Spain. E–F. Stream in Canuto de las Palas, Montes de Propios, Jerez de la Frontera, Cádiz, Spain (MNCN 15.05/94751). G–H. Stream in Canuto de la Gallina, Montes de Propios, Jerez de la Frontera, Cádiz, Spain. G. Operculum, inner side. H. Operculum, outer side.

Fig. 21. Protoconch and radula of Mercuria carrillorum Miller, García-Guerrero & Ramos sp. nov. from the stream in Canuto de las Palas, Montes de Propios, Jerez de la Frontera, Cádiz, Spain. A. Details of the protoconch. B. Protoconch nucleus. C. Protoconch microsculpture. D. Overview of radular teeth rows. E–F. Detailed view of the central and outer marginal teeth, respectively.

Fig. 22. Anatomy of Mercuria carrillorum Miller, García-Guerrero & Ramos sp. nov. from the stream in Canuto de las Palas, Cádiz, Spain. A–B. Female genitalia. C–D. Penis. E. Penis and head. F. Prostate gland. G. Ctenidium and osphradium. H. Stomach. I. Perioesophageal ring.

Fig. 3. Principal components analysis plot for species of Mercuria Boeters, 1971 based on 21 coordinates (9 landmarks and 12 semilandmarks). Each dot on the plot represents the consensus of the shape of each of the sampled populations. Warp grid deformations (TPS) show expansion (in red colour) and contraction (in blue) of the shell shape.